Implantable body transducers have recently been utilized in the medical sciences. An example of such a transducer is a pressure measuring transducer for measuring dura pressure, pressure within the heart, and other fluid pressures at various locations throughout the body. A common type of pressure measuring transducer utilizes an L-C oscillator having a resonant circuit comprising a fixed L and a variable C. The variable C consists of a capacitor having a fixed capacitive electrode and a movable capacitive electrode in the form of a stiff pressure responsive diaphragm, the output frequency of the oscillator being a function of the pressure sensed by the diaphragm. Thus, as the pressure surrounding the transducer varies, the capacitance of the capacitor changes due to deflection of the movable capacitive electrode, thereby resulting in a change in the output frequency of the L-C oscillator. A signal related to the L-C oscillator output is inductively coupled to an external processing device which converts the received frequency to a pressure indication. A problem inherent with these systems has been obtaining an accurate calibration of capacitive change as a function of pressure variation. Since very small movements of the movable capacitive electrode are experienced as the fluid pressure changes, an accurate interpretation of the L-C oscillator output frequency as it relates to pressure changes is essential. This calibration requirement has been conventionally met in one of two possible ways. The first way has been to individually calibrate each of the variable C's during fabrication of the transducer, and then to provide calibration curves to the doctor implanting the transducer in a patient. One problem with this technique is that the transducer cannot be effectively utilized at a location remote from the implanting doctor's records. The second way, and one more commonly used, is for each manufacturer to standardize the characteristics of each of his transducers so that a single standardized calibration curve will apply to all of a specific transducer model. This technique has been employed to some success; however, the cost of modifying each variable capacitor to meet certain predetermined performance characteristics has proven to be very expensive and has raised the cost of the transducers considerably. An additional problem with this method is that the standardized curve still must be available to each doctor attempting to utilize the transducer. Another problem has been that calibration curves vary as a function of unknown internal variables such as temperature. Thus, there is a need to provide a calibration means for implantable pressure measuring transducers, and a means for monitoring internal variables, which is contained within and can be recovered from the transducer itself, and which will be immediately available to any doctor at any location in which the transducer is to be utilized. The present invention provides such a calibration means.